This invention relates to a training device for use with a night vision device and more particularly, a filter arrangement which can be used to simulate night time conditions during daylight.
As is well known, the term night vision devices include direct view systems employing image intensification. Such systems have various uses but in general, enable night time vision by responding to low level radiation which is present at night to enable a user to visually perceive a scene or object in the nightime or in extremely dark environments.
Essentially, night vision devices employ an image intensifier or similar tube. The function of the image intensifier is to multiply the amount of incident light received by it to produce a greater signal for application either to a camera or directly to the eyes of a viewer. As such, these devices have both industrial and military application. Examples of early uses of such devices can be had by reference to a text entitled "Photo Electricity and its Applications" published in 1949 by John Wiley & Sons. Chapter 18 entitled "Light Beam Signaling and Infrared Detection" shows examples of early night vision devices such as the "Sniperscope" and "Snooperscope." Such devices are employed by the Military to enable troops to perceive the enemy at night. In any event, the chapter further discusses various peace time uses.
The development of such devices has followed the strides made in the electronic technologies. The apparatus' as presently employed for night vision are extremely small and compact. Hence, various companies such as the Assignee herein produce a number of devices such as night vision goggles for enabling one to accomplish night viewing. The Assignee herein supplies night vision goggles as No. F-4907 manufactured by IT&T Electro-Optical Products Division of Roanoke, Va. These devices will enable one to perceive at night with great acuity and perception.
It is however, important for the user to practice with the devices under supervision during the daylight before attempting to use the device in nighttime operation. This is especially true in military applications or in other specified activities, such as flying aircraft, driving or weapons operations. In this manner, the person employing the goggles is trained by a qualified assistant who monitors the operation while the goggle user learns to perceive according to the particular characteristics of the night vision device. Hence, it is extremely desirable to provide an apparatus which can simulate night conditions over a wide range of illumination levels.
It is therefore an object of this invention to provide an aid to be used in conjunction with a night vision device which is capable of reducing the ambient light reaching the night vision device to a level equivalent to nighttime conditions such as starlight, overcast moonlight, or direct moonlight. This enables a user to be trained in operating the night vision device under supervision occurring during the daytime.